问题 选择题

2A直流电流通过电阻R时,t秒内产生的热量为Q。现让一交变电流通过电阻R,若2t秒内产生的热量为Q,则交变电流的最大值为(     )

A.1A

B.2A

C.A

D.A

答案

答案:B

题目分析:据题意,对直流电有:,对交流电有:,联立解得:

,即,故选B。

阅读理解

阅读理解。

     Have you ever wondered what kinds of music young people across the United States are listening

to?  Are they crazy about Britney Spears? Do they love the Backstreet' Boys? Or do they dance with 

Eminem?  

     Well, nearly 6000 teens have taken part in a Teen & Music survey, made by USA Weekend

Magazine last autumn. And the result showed what types of music are hot and what are not.   

     It comes without surprise that hip-hop and rap are the most popular types of music among

American teenagers. They began in the mid-1970s with young black kids in New York, taking music

onto the streets. Hip-hop' and rap are well known for the break-dancing that goes with them.

     The word "rap" comes from a slang word. It is a rapid thyme that is spoken rather than sung.

Pop music, such as Britney Spears and the Backstreet Boys, has always met the tastes of the general 

public. It continues to enjoy support from teens and is the second most popular music after

hip-hop and rap.  

     The third is rock music with exciting dance beats and simple lyrics that speak loudly of social

problems. The melodies are led by electric guitars. Rock became popular in the US in the early 1950s.

The American singer Elvis Presley and British group the Beatles became world famous rock artists.

     The survey also showed that jazz is least loved by American teens. It developed in the later part of

the 19th century from a mixture of African work songs and hymns. Jazz tends to be the type of music

that people enjoy more as they get older. 

1. The Teen & Music survey was made by ____.

A. teenagers

B. teens        

C. USA Weekend Magazine

D. Backstreet Boys 

2. American teenagers like ____ best.        

A. hip-hop and rap

B. pop music        

C. rock music

D. jazz  

3. Britney Spears and the Backstreet Boys belong to ____.        

A. pop music

B. hip-hop        

C. rock music

D. jazz 

4. In the later part of the 19th century ____ developed.

A. rap

B. jazz    

C. the Beatles

D. the electric

5. This passage mentions at least ____ kinds of music in America.    

A. three

B. four    

C. five

D. six

问答题 简答题